System of illumination



Aug. 26, 1930. H. c, SINGLETON SYSTEM OF ILLUMINATION Filed March 18,1927 IHummotm-n l'ntensibg.

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8 m m M Q Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE HAROLD O.SINGLETON, OF SCOTIA, NEW YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK SYSTEM 01* ILLUMINATION Application filed March18, 1927. Serial No. 176,563.

The present invention relates to a system of illumination, and moreparticularly to an arrangement for illuminating sign-boards locatedalong public highways.

5 It is one of the objects of my invention to provide a system ofillumination in which the lamps for illuminating a'sign shall beenergized only when the sign is no longer visible by daylight and onlywhen a vehicle displaying light approaches or passes the sign.

It is a further object of my invention to provide a circuit arrangementemploying an alternating current source of supply for controlling theoutput of a pair of reverselyconnected photoelectric cells.

In carrying the invention into effect, a lamp or seriesof lamps areplaced adjacent the sign-board. The energization of these lamps iscontrolled by means of a pair of light sensitive cells, one of which isplaced adjacent the highway and pointed in a direction so as to beaffected by the headlights of oncoming vehicles. The latter cell may beplaced at any convenient point with respect to the signboard. The secondlight sensitive cell is employed to balance the effect of daylight onthe first cell and thereby prevent the energization of the lamps duringdaylight hours. It may be placed in any suitable position where it willbe subjected to the action of daylight, but unaffected by the lights ofpassing vehicles. By the use oftwo light sensitive cells in this mannerthe sign-board is illuminated only after dark and only when automobilesor other vehicles provided with illumination and traveling in onedirection pass or approach the cell which is adjacent the highway.

The novel features which are characteristic of my invention are pointedout with particularity in the appended claims. My invention itself,however. will best be understood from reference to the followingspecification taken in connection with the accompanying drawing in whichFig. 1 shows diagrammatically a circuit organization cmploying a sourceof alternating current whereby my invention may be carried into effect,while Figs. 2 and 3 show respectively charaeteristic curves of thephotoelectric cells,

and curves showing the relation between the intensity of illuminationand current in the two cells.

Referring more particularly to the drawmg, I have indicated at 1 and 2 apair ofvacuum type photoelectric cells connected to the secondarywinding 3 of a transformer 4, and reversely connected to the grid orcontrol element 5 of an electron discharge device or tube 6. The cathode7 of tube 6 is supplied with current through a secondary winding 8 oftransformer 4, the mid-point of winding 8 being connected to a tap 18 atone side of the central point of winding 3. 1

The output circuit of tube 6 includes the primary winding of atransformer 9, the secondary winding of which is connected to thecontrol electrode or grid of an amplifier tube 10. The cathode 11 ofamplifier 10 is connected in parallel with the cathode 7 while theoutput circuit of the amplifier includes a time delay relay 12 adaptedto actuate a switch 13 and close a circuit for a series of lamps 14arranged adjacent a sign board, not shown. Cells 1 and 2 are bothsubjected to the action of daylight. Cell 1, however, is alone affectedby the lights of passing vehicles, cell 2 being positioned so as to beunafi'ected by such lights.

It will be evident that the photo-electric cells 1 and 2 together withthe coil 3 constitute an electrical bridge, the path between the grid 5and the filament 7 being effectively connected to opposite pointsthereof. When current is induced in coil 3 such that the right-hand endis positive, this current will pass through the photo-electric cells 1and 2 in series. However, the voltage drop V between the negative end ofthe coil and the tap 18 transmits a negative charge to the grid 5, whilethe voltage drop V between the tap Y 18 and the right-hand or positiveend of the coil produces a positive charge on the grid. Inasmuch as thefilament 7 is not connected to the mid-point of coil 3 but to the leftthereof, the voltage V preponderates over the voltage V hence giving tothe grid a net positive charge so that when the cells are activatedduring daylight a pulsating current will flow in the output circuit oftube 6 and through the primary winding of the transformer 9. The cells 1and 2 t ius carry equal amounts of circulatory current which traversesthe entire coil 3 due to their series relation but pass unequal amountsof charging current flowing to the grid 5 due to the unsymmetricalposition of the tap 18 in the grid circuit. Both photoelectric cells areoperated on the flat portions of their charac teristic curve asindicated in Fig. 2, and as a result fairly wide fluctuations in thevoltages applied to the cells produce very little change in the currentthrough the cells.

With the connections shown, a positive potential will be simultaneouslyapplied to the anode or plate members 15 and 16 of tubes 6 and 10,respectively. When current flows in the output circuit of tube 6,however, the secondary oi transformer 9 is so connected that a negativepotential is supplied to the grid 17 of tube 10. If grid 5 is positive,as during daylight, full anode current flows through the primary windingof transformer 9. The maximum negative potential 1s, therefore,simultaneously applied to the grid or control element 17 of tube 10, andas a result current does not flow through relay 12, and lamps 14 are notilluminated. After daylight, the photoelectric cell 1 is alone subjectedto the action of light from passing vehicles. \Cell 2 remains dark and,there tore, offers a very high resistance to the passage of current.When light is directed onto cell 1, at this time, electrons flow fromthe cathode to the anode member of the light sensitive cell and to grid5, thereby tending to produce a negative charge on the grid Thepulsating current which now flows 1n the output circuit of tube 6,together with the negative potential which is applied to grid 17 of tube10, are greatly reduced in value. As a result, current flows in theoutput circuit of tube 10, and switch 13 is actuated, thereby closing acircuit for the lamps 14.

In the operation of the circuit described, it will be noted that duringone half of the alternating cycle, when the anodes of tubes 6 and 10 arepositive with respect to their associated filaments, thephotoelectriccells 1 and 2 will have the proper polarities applied to theirelectrodes. During the succeeding half cycle of the alternating currentwave, the anodes of tubes 6 and 10 are both negative, and the tubes donot conduct any current. The grids of tubes 6 and 10 are, therefore,biased properly during the half Wave whe the anodes l5 and 16 arepositive, and it is, of course, immaterial what potential is applied tothe grid elements of the tubes during the succeeding or negative half ofthe alternating current wave, since at this latter time the tubes 6 and10 are both non-conducting.

The relay 1? included in the output circuit of the amplifier 10 is sodesigned that the circuit for lamps 14 remains closed for a definitetime interval after light from a passing vehicle has been directed ontothe li ht sensitive cell 1, or until the vehicle has liad time to passthe sign-board.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is:

1. A system of illumination comprising an electric lamp and an electrondischarge device having input and output circuits, means responsive tothe flow of current in the output circuit for controlling a circuit forsaid lamp, a pair of light sensitive cells connected in said inputcircuit, and means whereby one of said cells operates to prevent theflow of current through the output circuit when substantially equalamounts of light are directed onto both cells, said electron dischargedevice and light sensitive cells being energized by alternating current.

2. A system of illumination comprising a lamp, a circuit therefor, meanscontrolling said circuit, said means including a light sensitive celland means for balancing the effect of said cell, an electron dischargedevice comprising an anode, cathode and control electrode, a connectionfrom said cell to the control electrode, and means whereby analternating potential may be simultaneously supplied to said cell andbalancing means and to the cathode and anode of said discharge device,the potentials applied to said cell and balancing means being unequal.

3. A system of illumination comprising a lamp, a circuit thcrcior, meanscontrolling said circuit. said mcnns including a circuit comprising apair of reverscly connected light sensitive cells, an electric dischargedevice including an anode, cathode and control electrode, a connectionfrom said second-mentioned circuit to said control electrode, a secondelectron discharge device comprising an anode, cathode and controlelectrode, means in the output circuit of said first-mentioned dischargedevice for controlling the potential of the control electrode of saidsecond device, means in the output circuit of the second electrondischarge device for controlling the first-mentioned circuit, and meanswhereby an alternating potential may be simultaneously applied to saidfirst-mentioned circuit and to said electron discharge devices.

4:. In combination, a circuit including a light sensitive cell andbalancing means therefor, an electron discharge device comprising ananode, cathode and control electrode, a connection from said cell tosaid control electrode, a source oi alternating current, connectionsfrom said source to said cathode, anode and circuit, said connectionsincluding means whereby unequal potentials may be applied to said celland balancing means.

5. In combination, a circuit including a pair of reversely connectedlight sensitive cells, an electron discharge device comprising an anode,cathode and control electrode, a connection between said cells and thecontrol electrode of said discharge device, a source of alternatingcurrent and connections from said source to said anode, cathode andlight sensitive cells, said connections including means whereby unequalelectrometive forces may be applied to said light sonsitive cells. 6. Incombination, a pair of reversely connected light sensitive cells, meanswhereby light may be directed onto said cells, a pair of electrondischarge devices each com rising a cathode, anode and control electroe, a connection from said light sensitive cells to the control electrodeof one of said devices whereby variations in the current through thecells may produce corresponding variations go in the potential of saidcontrol electrode,

means in the output circuit of said one device for controlling thepotential of the control electrode of the other discharge device, asource of alternating current and connections from said source to thelight sensitive cells and to the cathodes and anodes of the dischargedevices.

7. In combination, a pair of light sensitive cells energized by a sourceof alternating 80 current and containing a cathode and an anode, meanswhereby light may be directed onto said cells, a plurality of electrondischarge devices each having a cathode, anode and control electrode,the anodes of said de- 85 vices being so connected to the source ofalternating current that they simultaneously have the same polarity, aconnection from the anode of one cell and from the cathode of the othercell to the control electrode of one 40 of said discharge devices, andmeans in the output circuit of said one discharge device for controllingthe potential applied to the control electrode of the second dischargedevice.

46 8. In combination, apair of light sensitive cells, each containing acathode and an anode, a winding adapted to be energized from analternating current source for supplying the cells with energy, aplurality of electron discharge devices each having a cathode, anode andcontrol electrode, a connection from one end of said winding to each ofthe anodes of said devices, a connection from the cathode of one celland from the anode of the other cell I to the control electrode of oneof said devices, and a connection from said winding to each of thecathodes of the electron discharge devices and to the control electrodeof said other discharge device. 7

'0 In witness whereof, I have hereunto set my hand this 16th day ofMarch, 1927.

HAROLD C. SINGLETON.

